Means for reducing cross fire in telegraph circuits



April 13 1926. 1,580,191

J. M. FELL MEANS FOR REDUCING cRdss FIRE IN TELEGRAPH CIRCUITS FiledApril 27, 1922 IN V EN TOR.

' ATTORNEY ing current Patented Apr. V

UNI ED STA TES OHN M. FELL, 0E HACKENSACK, NEw JERSEY, AssreNon TOAMERICAN TEL rnoNE AND TELEGRAPH COMPANY, A conroRA'rroN OF NE YORK.

MEANS FOR REDUCING onoss FIRE-IN TELEGRAPH omcurrs.

Application filed April 27, 1922. Serial- No. 556,876.

To all/whom itmaz comer-n: I

Be it known that 1, JOHN VMMFELL, a citizen of the UnitedStates,resldingfat Hackensack, in the county of Bergen and- State of NewJersey, have invented certain Improvements in Means for Reducing CrossFire in Telegraph Circuits, of whiclrthe following is a specification.

This invention relates to means for'neutralizing cross-lire in groundedtelegraph cir- ;cuits, and particularly to an arrangement to neutralizeelectrostatic cross-fire in the disturbed circuits of a system, due to.potential changes in the. disturbing circuit.

In the transmission of signals -over a grounded telegraph circuit whichforms one or a group of circuits extending substan tially parallel toeach other, currents of an interfering nature are set up in the othercircuits of the group by virtue of the mutual admittance between thevarious circuits.

When the disturbing line has its potential changed in apositivedirection, as on the closing of the line dueto a marking signal sentfrom the home end, i. e.,' the end having a positive line battery, theinterfercuits. Here it divides and flows towards eaclrend of the saidcircuits, the magnitude of the currents in 1 the two directions pendingon the magnitude of the impedance at each of these circuits from its'midpomt to the groundingpoints'at its ends. As the potential along thedisturbing'line is restored to its original value and direction, whichoccurs on the opening of the line whena spacing signal is sent from thehome? end, the interfering current will reverse and Wlll flow in thedisturbed circuits from their grounded ends, towards their thence to thedisturbing line. The direction of flow is reversed in each of the abovedescribed cases when marking and spacing signals respectively are sentfrom the dis tant end of the disturbing line-which has a batteryoppositepolarity to that of the lhome? end discuss'e above. 1 Y

7 These interfering currents atl'ectthe relays or othersignalresponsive'apparatus at the terminals of the disturbed circuits,and im- Pair transmission. U

It'is flows towards the disturbed cirmidpoints and the object ofthisinvention tolneutralize the efiect of interfering currents upon,

the signal-responsive apparatus at the terminal circuits by transmittingsimultaneously through such apparatus neutralizing cur. rentsoppositein. direction and su-bstantially equal in value to the interferingcurrents.

;This invention will be better understood from the following descriptionwhen read in connection with the attached drawing, of which Fig. l'shows a form of embodiment of the invention in' which neutralization-isefl'ected by means of an inductive coupling between theleak circuits ofthe various line circuits, and Figs. 1 and l show the poten- -t1'algradients for various operating conditions; Fig. 2- shows an arrangementusing polarized'relays in the leak circuits to effect neutralization,and Fig- 8' shows the use of neutral relays to e'flect't-he desiredresult.

In'Fig. 1, 1 and 2 represent two line circuits having connectedtherewithmeans for effecting the desired neutralization which constitutes oneform of the invention. Any number of line circuits might be sointerrelated but the description will be simpler and clearer if confined.to two line circuits and their associated apparatusas shown in thefigure;v The line circuit 1' has'connected therewith at station X a key3, a battery 4, a'line relay 5,;and a current limiting resist ance 29.Similarly, at station Y there are connected' to the circuit 1 a key 6, ab'attery 7, the polarity of which is opposite to battery I t,-a linerelay 8, and a current limiting re- I sistance 31, Theline circuit 2has, connected therewith at station X a key 9, a battery 10, a linerelay11 and ,a current limiting resistance 30, and similarly at station Y akey 12,-a battery 13, the polarity of which is 'oppositejthatof battery10, a line relay 14. and a current limiting resistarice32. Themutualadmittance is representedby a con denser K connected by dottedlines between the two line circuits, Eacholf the said line circuits hasconnected therewith aleak-circuit tofground. Thus, at, station"X,;;line

'1' has connected therewith a resistance'lS in series witlrthe condenser'l9 and. one of the windings 16 of a transformer 15; and similarly line2 has connected therewith a resistance QOinseries with acOndenser-Ql,

and. the winding 17 of the transformer VA similar neutralizingtransformer 22 is connected with the leak circuits at the station Y. Oneof the windings 23 of this transformer-is connected in series'with theresistance 25 and the condenser 26, and the other winding 24: in serieswith the resistance 27 and the condenser 28.

Having in mind the foregoing description of the circuit the inventionwill be clear from the following description of its mode of operation.

For the purpose of description let it be assumed that signals are beingtransmitted over the line 1 at a time when the line 2 is unoperated,that is to say, when the keys 9 and 12 are closed. Not only will thisresult in grounding both terminals of the line circuit through thebatteries 10 and 13, but a steady current will flow over the line 2.This will produce no abnormal effect upon the signal apparatus connectedwith this circuit. However, as a result of the transmission of signalingimpulses over the line circuit 1, interfering currents will be set up incircuit 2 which it is the object of this invention to neutralize so thatno effectwill be produced by them upon the signal receiving apparatus.Furthermore, let it be assumed that the key 3, connected with the line1, is closed to transmi-t'a marking signal to the distant station Y.Just prior to the closing of this key the line circuit 1 was at adefinite negative potential, represented by the dash line ain Fig. 1sincethe negative battery 7 remained connected to the line. By theclosing of the key 3 the potential of the end of the line near X waschanged from a negative value to a positive value so that the potentialgradient along the line 1 is represented by the line Y) in Fig. 1. Itshould be observed that the potential change which is represented by thedistance between a and b is quite large near station X and diminishestoward station Y so that the effect of this changing potential, whichmanifests itself in the current flowing in line 2, is greater nearstation X than near station Y. The effect of impressing the positivepotential upon line 1 by the closing fthe key 3 will cause aninterfering current to flow to line 2, which is represented by the wavyarrow, which interfering cur rent will divide and flow to ground at eachend of the line 2. A

This interfering current would normally produce an effect upon therelays 1-1 and 14- unless it were neutralized, which may be effected asfollows: When the signaling impulse was transmitted over line '1 by theclosing ofthe key 3, current flowed through the leak circuit of line 1to ground, containing the winding 16, in the direction shown by thesolid arrow. The winding 16 bears such relation to the winding 17 thatthe potential induced therein will cause 2.

flow of current in the direction represented by the dotted arrow. Theestablishment of this difference of potential in the winding 17 willcause a flow of current in the circuit containing the battery 10, key 9,relay 11, resistances and 20, condenser 21 and Winding 17. The directionof this flow of current will be as represented by the dotted arrows. itwill be seen, therefore, that this neutralizing current opposes theinterfering current in relay 11 and thereby minimizes "the eiiect of theinterfering current upon this relay. The induction of the potential inthe winding 1? will also cause a flow of current in the directionrepresented by the dotted arrows through a circuit containing thebattery 13, key 12, relay 1%, resistance 32, line 2, resistance 20,condenser 21 and winding 17, to ground. The direction of this current isin opposition to the interferin currentflowing through the'relay 14 andtends to neutralize the interfering current. The neutralizingtransformer 22 will also come into play and produce a neutralizingcurrent which will tend to neutralize the interfering current, althoughthe magnitude of this current will be smaller than that produced by thetransformer 15, since the change of potential in the line 1 is smallerat station Y than at X. This is clearly seen from the curves a and Z) ofFig. 1. The How of current through the winding 23 will be in thedirection represented by the solid arrow, which will induce a differenceof potential in the winding 24, which will cause current to flow in thedirection represented by the dotted arrow. The direction of this currentwill be such as to tend to neutralize the interfering current.

1f the key 3 is open for the transmission of a spacing signal, thepotential gradient of line 1 will change from b to a. This re sults in achange of direction of the interfering currents in the line 9., that isto say, the interfering current will flow from the ground at each end ofthe line 2, and through the admittance to the line 1. This change in thedirection of the interfering current is met and counteracted by thechanging of the direction of the neutralizing current. By the opening ofthe key 3 the potential across the condenser 19 is varied so thatcurrent will flow through the winding 16 in direction opposite .to thatshown by the solid arrow in the drawing. This will result in theinduction of a potential in the winding 17, adapted to produce a currentopposite indirection to the dotted arrow shown in the drawing, In likemanner, the direction of current in the windings of the neutralizingtransformerQQ is changed so that the neutralizing currents in the linecircuit are opposed in direction to the interfering currents.

Fig. 1 shows the potential gradients for the condition that key thereception of signals transmitted by opening and closing of the key'G atstation Y. Under this condition, the line 1 remains the disturbingcircuit and the line 2 the disturbed circuit. The greatest effect,however, would be produced, under this condition, near the station Ybecause the greater variation of potential differencebetween the linecircuit and ground occurs near Y. The manner in which neutralization iseffected is, howevensimi-lar to that previously described. p I

The neutralizing transformers may be located at a central point in theline, or at each terminal, as shown inthe drawing. The central locationwould probably be most eflicient as the neutralizing impulses would thendivide between the two terminals in about the same proportion as theelectrostatic cross-fire impulses are divided. 'VVhen, however eneutralizing transformers are located: ="lihe terminals it isadvantageous to operatethe telegraph circuits with higherbatterylpotentials andto limit the currents by means of the resistances29, 30,'-etc.," located" between the battery and the; trans- 5 formerbranches. Not only has this the 'effect of placing the transformernearer the center of the' line but it possesses advantages from thestandpoint of practical operation. The transformer branches maypermanently to the Morse branches of comor they may be made a'componentpart of the compositeset. In either case, they would tend toneutralizeelectrostatic cross-fire in any telegraph system'op positesets,

erated on a composited :circuit. Although I the invention is shownconnectedwith asingle'line Morse circuit, it s adapted for use in.connection with duplex or half-duplex circuits. And as has beenstated'heretofore,-

the invention isapplicable to thene-ut'ralization of cross-fire in anynumberof circuits exposed to asingle' disturbing circi1i t-.; Thus, forexample, it is possible to provide-a transformer having four windingsfor use with the four wires of a phantom quad circuit.

The arrangement shown in Fig. 2 employs the use'of polarized relaysforimpressing gneutrahzing impulses upon an exposed circuit forminimizing electrostatic cross-fire.

ln this figure, the same reference numerals have been used to representparts similar to those shown in Fig. 1. Connected with the line circuit1 is a leak circuit containing the condenser-19, a resistance 18 andthearmat-nre49. Similarly connected to line circuit 2 is a condenser 21,aresistance'20 and the armature 48. 'lVhen keys 3 and 9 are closed,

a current flows through the operating windings 44 and 46 of the relaysand'41 respectively to ground, whichinainta-ins the armatures'48. and'49 in position touching their right-hand contact-s, which connects thebe connected I By the closing of key The windings and 47 of the said"relays are adapted to move the armatures 48 and 49 to the left-handcontacts upon the opening of the circuits through the windings 4'4 and'46. The neutralizing relay circuit at. station Y is similar to that atstation X- and needs little further comment. It should be noted thatthe-batteriesconnectedvwith the left-hand contacts of the armatures 54and 55 at station Y- are of opposite polarity to similar batteriesshown, connected to the right-hand contacts 'of the armatures 48 and 49at station X. a I

When keys 6 and 12 are closed, which for example isthe situationexisting when signals arebe'ing received'at station -Y over line 1, andwhen line 2' is idle, current flows through the operating windings 50and 52 of 'remain operated regardless of changes in the line potentialcaused bythe operation of the keys at station X, so that the armatures-54 and 55 remain in the position shown, so long as the keys 6 and 12remain closed. Itis important that these relays should not respond tothe actuation of the distant keys, because, if they did, the batteriesconnected with the armatures would'impress'on the line circuitsimpulsesin the same direction as the batteries to the said armatures. I

interfering impulses, which therefore would tend to increase the,receiving end cross-fire instead of diminishing it. v I

When the key .3was closed, as shown in the figure, a signalingimpulsewas transmitted over the'line 1 in the direction represented by-thesolid arrows. This willproduce an interfering current in the line 2 inthe; di-

the wavy arrows. 3, current flowed through the winding 44 intlIGClIIGCtIODI'GP- rections represented by resented by the solid arrow,which brought 7 right-hand contact, thereby establishing acircuitincluding the battery 10, key 9, relay 11, condenser "21,resistance 20, armature 48. battery 62, which causes a flow ofneutralizthe armature.48 into "position touching' its ing'cu'rrent inthe direction represented by the'dotted arrows." Since there is butslight point where relay 42 is connected to the circuit as shown bythepotential gradients (a. and b of Fig. 1 the said relay will notrevariation of the potential difference at thel by the neutralizingcurrent, represented by the dotted arrow, which is created by theneutralizing difference of potential set up in the circuit controlled bythe relay l0 at station X.

It the key 3 is opeud for the transmission of a space signal, theinterfering current in the line 2 will be in direction opposite to thatrep-resented by the wavy arrows in the figure. By the opening of thesaid key, current will cease to iiow through the winding 44 of the relay40 and consequently the armature S will be moved by the lGlJlElCtlWZwinding 45 into a position touching its left-hand contact. This servesto ground "the leak circuit containing the condenser 21 and theresistance 20. The condenser 21 will accordingly give up its energy andthe flow of current therefrom will be in the direction opposite to thatshown by the dotted arrows in the figure, which direction will tend toneutralize the interfering impulse.

The arrangement shown in Fig. 3 is similar to that shown in Fig. 2 andneeds but little additional description. It represents the use ofneutral relays in place of the polarized relays shown in Fig. 2. Theseneutral relays 60 and 61 perform in the same manner the same functionsas are performed by the corresponding relays in 2.

It will accordingly be seen that by means of theinvcntion, which isshown in several forms of embodiment in the attached figures,electrostatic cross-lire between grounded telegraph circuits may besubstantially eliminated or greatly minimized.

Althoughthis invention has been shown as disclosed in particular torn isit is capable of embodiment in diii'crent forms without departing fromthe scope oi the appended claims.

What is claimed is:

1. In a grounded telegraph system comprising a plurality of singlelineMorse circuits, having grounded leak circuits inductively related toeach other, the method of neutralizing cross-lire between said Morsecircuits which consists in in'ipressing signaling impulses upon one ofsaid Morse cir cuits, allowing part of the signaling current to flow toground through the leak circuit of the said ll'lorse circuit, andinducing a current in other leak circuits in such direction as toneutralize interfering currentssct up in their associated Morse circuitsby said signaling impulses.

2. In a grounded telegraph system, the combination with two groundedtelegraph circuits of leak circuits individual to and connected with thesaid telegraph circuits, said leak circuits having a condenser in serieswith an inductance, the said inductances being mutually related.

In a grounded telegraph system, the combination with two groundedtelegraph circuits of leak circuits individual to and connectedtherewith, the said leak circuits being inductively coupled so that aflow of current in one will induce a current in the other of the saidleak circuits, the direction of the induced current being such as toneu-' tralize interfering currents set up in that telegraph circuit withwhich said other leak circuit may be connected.

l. In a grounded telegraph system, the

combination with a line circuit having grounded terminal circuitsassociafgd therewith, of a second line circuit also having groundedterminal circuits associated therewith, and a plurality of leak circuitsindivididual to and connected with the said line circuits, each of thesaid leak circuits having a condenser in series with .an inductance, thesaid inductances being mutually related.

In a grounded telegraph system, the combination with two groundedtelegraph circuits of a plurality of leak circuits individual. to andconnected with each telegraph circuit at each end thereof, each of saidleak circuits having a condenser, and each pair of said leakcircuits atthe same point on their respective line circuits being inductivelyconnected together so as to produce -neutralizing impulses wheneversignaling im pulses are transmitted overthe other of said telegraphcircuits.

6. In a grounded telegraph system, the combination with a plurality ofline circuits having grounded terminal circuits associated therewith ota plurality of leak circuits .individual to and connected with the saidline circuits, each of said leak circuits having a condenser in serieswith an inductance, all of said iudnctances being mutually related.

In testimony whereof, I have signed my name to this specification this25th day of April, 1922.

JOHN M. FELL.

